1. Field of the Invention
The invention relates to a biopsate holding device for a biopsy cannula to perform transcutaneous biopsies, in particular of hard tissue and bone marrow tissue, by means of a biopsate holding device that can be inserted into the proximal end of a biopsy cannula and pushed in between the inner wall of the biopsy cannula and the tissue-removing cylinder.
2. Description of the Related Art
The state of the art can be described as follows: Conventional needles for biopsic, transcutaneous removal of hard tissue, in particular bone marrow tissue, consist of a cylinder of different lengths and diameters, whose proximal end is fitted with a grip and whose distal end is tapered and narrows into a boring with a cutting edge. Is the needle pressed into the tissue and simultaneously rotated around its axis it cuts a cylindrical piece out of the tissue to be removed that is taken up in the hollow interior of the needle. Withdrawal of the cylinder from the tissues as biopsy requires the subsequent interruption of the connection of the distal cylinder end with the remaining tissues into which the needle has been inserted. For this purpose, in conventional methods the grip of the needle is set into vibrations that run in a plane at a right angle to the needle axis with a trocar being provided at the point of insertion into the tissue. As a result of this approach, the connections between the distal end of the biopsy and the remaining tissue are broken at the distal end of the needle that can be withdrawn and whose interior contains the biopsy material that is detained by the tapered end of the needle. This method of examination has the following disadvantages: Frequently the biopsy material is not retained in the needle since it is not completely loosened from the remaining tissue and since there is an, albeit low, negative pressure generated in the needle while it is being pulled out of the tissue so that the biopsy material is subsequently drawn in although this suction cannot overcome the opposite brake effect that is caused by the tapering of the needle end. All this makes the repetition of the entire biopsy examination necessary. Frequently the explained difficulties while the needle is pulled out cause the biopsy material to slip out of the distal end of the needle which may result in an injury and a rupture of the biopsy cylinder during the withdrawal through the tissue and a loss of parts of the distal portion of the biopsy. The movements or vibrations that are exerted onto the needle in order to separate the biopsy often cause smaller fractures at the surface and interruptions in the coherence of the hard tissue into which the needle was inserted, with this possibility being increased with the distance from the tissue surface. The results are in for the patient and damaging of the needle that is prone to become bent and thus lose its necessary straightness.
Known is also a patent DE 43 05 226 “Device for needles for transcutaneous biopsies” that describes an accessory device for conventional biopsy needles for transcutaneous tissue biopsy, in particular hard tissue and bone marrow tissue. The accessory device permits the trouble-free performance of biopsies at any tissue, from hard, compact bones to very thin and brittle bone marrow tissue, without the danger that the biopsy needle is withdrawn without a tissue sample. The accessory device reduces the danger of damaging tissues during a biopsy and mitigates pain in patients. The basic principle of the accessory device is that an insertion structure is inserted at the proximal end of the biopsy needle and pushes itself between the inner wall of the needle and the tissue cylinder. The cylindrical configuration of the biopsy cannula makes sure that this structure is clamped together to retain the biopsate. The disadvantage of this technical solution lies in the fact that the clamping of the structure subjects the retained biopsate to a press fit. This press fit causes crush artefacts of the biopsate. The conclusion is that the crush artefacts may distort the results of the subsequent examination of the biopsate.